The present invention relates to latching relay circuits and to analog to digital converters (A D C's) with range switching facilities. The invention is particularly, but not exclusively concerned with such converters employed as multimeters, that is to say meters capable of selectively measuring at least current and voltage.
It is known to provide a manual switch to effect range switching of an A D C; the switch controls a switched attenuator in the case of an A D C employed as a voltmeter and controls a switched shunt in the case of an A D C employed as an ammeter. It is also known to employ relays instead of manual switches and to control the relays automatically in response to the digital output in such a way as to cause the digital output always to lie within a predetermined range, e.g. within the range N/10 to N where N is the maximum digital output. This is known as autoranging, i.e. automatic range selection.
The relays consume a significant amount of power and this creates a problem in the case of a battery-operated A D C. One object of this invention is to provide a latching relay circuit which can be set to either state by an operating pulse and which latches in either state. The invention is also concerned with an improved autoranging A D C in which latching relays are employed.